Wide-range linearly estimation of blood flow with low sampling frequency using laser speckle contrast imaging

Laser speckle contrast imaging (LSCI) is a real-time, non-invasive imaging technique widely used for visualizing blood flow in biomedical applications. Likely, LSCI method can be applied to the myocardial coronary artery to monitor the evolution of blood flow on spatial and temporal scales, which is of large-size inner diameter, higher flow rate, and has thicker vascular walls. In this paper, we aim to measure wide-range blood flow rate linearly under static scattering noise. We elaborate on the differences between temporal and spatial static scattering parameter that are typically ignored but can result in inaccurate measurements of blood flow through phantom experiments. It is the first time, to our best of knowledge, that the maximum linear range can be measured up to 616 mm/s with 20 Hz sampling frequency. When the blood flow is covered by cardiac vascular tissue, the maximum linear blood flow range can be up to 92.4 mm/s with 100 Hz sampling frequency. Besides, we compared uniform light with ring-shaped light and demonstrated that the latter can increase penetration depth, thereby extending the linear range and reducing oscillations in the curve. Those results will greatly lower the expense of LSCI device while improving performance, and benefit future big animal clinical medical research, especially in monitoring the spatiotemporal evolution of coronary arteries in coronary artery bypass grafting (CABG) surgery.